The goal of this project is to identify effective constituents and mechanisms of green tea catechins (GTCs) in precancerous prevention of human breast cancers associated with long-term exposures to environmental carcinogens. Carcinogenesis of breast epithelial cells from non-cancerous to precancerous and cancerous stages is a multi-year, multi-step, and multi-path disease process with progressive genetic mutations. Environmental factors (exposures to chemical carcinogens, dietary habits, etc.) are part of that process and are responsible for more than 70% of human breast cancers. Clinically, the transformed breast cells involved in ductal carcinoma-in-situ (DCIS) are precancerous and can either develop into or raise the risk of invasive breast cancer. Therefore, it is important to develop effective strategies to identify preventive agents that block formation of DCIS as a target endpoint for early prevention of breast cancers. We have developed a precancerous cellular model that verifies the potency of carcinogens that cause breast cells to acquire distinct cancerous properties in an accumulative, stepwise, and exposure-dependent manner, mimicking formation of DCIS in culture. Epidemiologic studies have suggested that GTCs may prevent breast cancer. However, the abilities of GTCs to block precancerous carcinogenesis of human breast cells have not been addressed, representing a serious gap in our understanding of the use of green tea to prevent these types of human breast cancers. Our central hypothesis is that the carcinogen-induced cancerous properties can be used as target endpoints for identification of GTC constituents and mechanisms in suppressing carcinogenesis of human breast cells. To address this hypothesis, we will use our cellular system to: 1) identify GTC constituents that block biological and biochemical target endpoints, and 2) identify transcriptomic target endpoints for GTCs in the prevention of precancerous carcinogenesis of breast epithelial cells. Success of this project will lay the groundwork for identifying biological, biochemical, metabolic, and molecular mechanisms for GTCs in the prevention of precancerous carcinogenesis of breast cells, and formulating designs for the clinical studies of dietary agents in the precancerous prevention of human cancers caused by environmental carcinogens. Our paradigm serves as a new, time- and cost-efficient approach for identifying dietary agents that are capable of blocking precancerous carcinogenesis of human breast epithelial cells and delineating their mechanisms for prevention of carcinogenesis. The broad impact of this project will benefit the whole of society by scientifically identifying active dietary agents to be used to formulate diets and dietary supplements that reduce the health risk of breast cancer and other cancers resulting from long-term exposure to carcinogens in environmental pollution. PUBLIC HEALTH RELEVANCE:Our paradigm serves as a new, time- and cost-efficient approach for identifying dietary agents that are capable of blocking precancerous carcinogenesis of human breast epithelial cells and delineating their mechanisms for prevention of carcinogenesis. The broad impact of this project will benefit the whole of society by scientifically identifying active dietary agents to be used to formulate diets and dietary supplements that reduce the health risk of breast cancer and other cancers resulting from long-term exposure to carcinogens in environmental pollution.